create alias onepunch_man -> one_punch_man
create alias onepunch-man -> one_punch_man
create alias one-punch_man -> one_punch_man
This, to me, seems the most visually neutral format for the tags, in light of varying compounds and hyphenations. This double-spaced format is, at least, seen during the anime's commercial bumps, to justifying using it at all.
EDIT: Preference to NWF_Renim's request below.
Updated